Labyrinth packing for turbines



Aug. 25, 1931. MOODY 1,820,150

LABYRINTH PACKING FOR TURBINES Filed Sept. 15, 1920 3 Sheets-Sheet l U 8M'UlzM l'o'e', 333% abl mme lg Aug. 25, 1931. F. MOODY 1,820,150

LABYRINTH PACKING FOR TURBINES Filed Sept. 15. 1920 3 Sheets-Sheet 2 16;6 WWW Aug. 25, 1931.

L. F. MOODY LABYRINTH PACKING FOR TURBINES Filed Sept. 15, 1920 3Sheets-Sheet 3 Patented Aug. 25, 1931 UNITED STATES earaur orrica LEWISFERRY. MOODY, OF PHILADELPHIA, PENNSYLVANIA LABYBINTH PACKING FOBTURBINES Application filed September 15, 1920.

reducing the leakage of water between the runner and the surroundingstationary parts of a. rotary hydraulic machine, and more particularlythe provision or" such apparatus in hydraulic turbines; and at the sametime to provide means for reducing the axial thrust of the water uponthe runner. Another object of this invention is to provide suchapparatus so formed as to avoid extremely small clearances, and thus toreduce the risk of clogging by foreign matter carried by the water andthe danger of injury from rubbing between the parts. These and otherobjects will be understood upon consideration of disclosures of severalspecific examples embodying the invention. It will be understood thatmodifications may be made within the scope of the invention.

In the accompanying drawings illustrating the invention Fig. 1 is asectional elevation through the axis of a vertical shaft hydraulicturbine.

Fig. 2 is an enlarged view of a detail of Fig. 1 slightly modified.

Fig. 3 is a sectional view of another embodiment of the invention, and

Fig. 4 is an axial section of another turbine embodying the invention.In the embodiment of the invention shown inFig. 1 an entrance volute 5guides the flow to the adjustable guide vanes 6 directing it onto thevanes of the runner R having shaft and discharging into the drafttube T.A

cover casting 7 carries bearings for the shaft S and the stems 10 ofadjustable guide vanes 6. ,The runner R is formed with cylindricalridges A machined upon its crown and band with intervening circulargrooves B between the successive ridges. Into these grooves projectcorrespondng ridges formed upon stationary plates C and D bolted to thesurrounding portions of the turbine structure. Inthe design shown, thecrown and band of the runner and the plates C and D are so formed thatthere are six points of contracted area through which the leakage watermust flow to escape either above or below the runner, the first point ofcontraction being Serial N0. 410,454.

the simple straight seal formed between the runner periphery and plate.The water flowing through these points of small clearance will acquire aconsiderable velocity due to the pressure head existing in the spacebetween the guide vanes and runner. This velocity will, however, bematerially lower than it would be if a single point of small clearancewere employed. If there were only a single clearance point, the waterwould acquire at such a point a velocity proportional. to the squareroot of the entire pressure producing the "leakage flow, By using amultiple arrangement of seals such as here shown the pressure headproducing the leakage flow is sub-divided into a series of stages (heresix) so that the velocity of flow becomes proportional to the squareroot of the pressure drop through only one stage, or I in this case,one-sixth of the entire pressure producing the flow. Without consideringother features of the device, therefore, the ar singing of a numberofcontractions in series materially reduces the flow throu h the seal.In addition to arranging a num er of seals in series a suddenenlargement is left in the groove between each two seals in which a lossof head is imposed-upon the leakage flow due to the dissipation ofvelocity head, and these enlargements are so formed as to facilitate theproducing of an eddy or eddies in the water filling the space. Justas-it is important to avoid in the main fiow ofthe water through theturbine any points in the water passage where eddies are likely to beformed, it is correspondingly important to introduce wherever possiblein the passage through which the leakage water must fiow, spaces inwhich eddies may fornn Another purpose of the enlargements betweensuccessive seals is to provide a considerable body of Tater capable ofmomentarily absorbing any heat produced by friction if local rubhingshould occur between the rotating and stationary surfaces.

After the leakage water has passed through the clearances, the waterabove the runner R flows into the spaces between the head cover plate 9and the runner disc 11, and the; water flowing below the runnerdischarges into the l d Hi draft tube T. In order to reduce the discfriction on the runner, the width of the space between the runner crown11 and the cover plate 9 and that surrounding the runner band is madesmall to reduce to a minimum the body of water in said spaces and boththe runner and surrounding parts are given smooth circular contours withas little surface exposed to the water as possible. Since the waterwhirling in the space between the runner and head cover will tend to setup centrifugal pressures increasing toward the outer periphery, reliefholes h are provided at or near the outer periphery of the spaces,through which the water may escape and thus relieve the pressure uponthe runner, thereby reducing the hydraulic thrust which must be carriedby the thrust bearing supporting the rotating parts of the unit. In thearrangement shown in Figure 1 the leakage water flowing through holes itabove the runner escapes through the pipe at F which is a drain leadingto the tailwater.

Another method of relieving the thrust, and one which forms incombination with the arrangement of seals described above an essentialpart of this invention, is shown in Figure 3. In this figure a modifiedarrangement of seals A B is shown, there being four points of smallclearance at top and bottom of the runner instead of six. An arrangementof seals more like that of Figures 1 or 4 could be used in Figure 3where desired. In the turbine here shown, llat liner plates 17, p areshown attached to the runner crown 8 and to the head cover 7respectively, the head cover 7' being formed with an inner wall carryingthe liner p. The liners are used for purposes of renewal in case of wearor corrosion, and may be used when desirable. The essential feature ofthis rrangenient as the stationary plate P forming part of the headcover, and located adjacent to the runner crown 8. This plate isconnected to the upper wall of the head cover 7 by radial vertical ribs1". The plate at its inner periphery forms a running clearance or sealwith an extension of the runner hub u. Near the outer periphery of thespace between the runner crown and the inner plate of the head cover,relief holes h are placed connecting with the space between the twowalls of the head cover. The tendency of the water within the spacebetween the runner crown and the lower plate of the head cover to set upcentrifugal pressure is avoided by these relief holes which permit theleakage flow to be bypassed through the head cover and thence downthrough openings H in the runner hub into the center of the draft tubeT, a point where low pressure exists. The vertical ribs 1 forming partof the head cover prevent any whirling of the water within the headcover, and thus avoid imposing a contrifugal force obstructing the flow.The small clearance or seal between the extension at of the runner huband the inner periphery of the lower head cover plate P prevents a.return of the water into the space between the runner crown and headcover. If such a return were permitted, there would be a secondarycirculation set up which would absorb a considerable amount of energyand which would also impair the relief of the pressure on the runnerdisc provided by this device.

The special arrangement of seals A, B when used in conjunction with themethod of pressure relief just described cooperates with it to make thecombination effective. If a single seal were used, the high rate ofleakage would impair the action of the remainder of the device,particularly after the turbine has been in use for a considerable time,and wear due to either rubbing or cutting produced by the high velocityof flow has taken place. A large quantity of water flowing through therelief holes would result in a back pressure, and end thrust on therunner would be caused.

In Figure 3 the leakage water at the top of the runner passes through arelatively tortuv one and restricting seal A, B, to the chamher betweenthe wearing plates 1), p. The pressure in this upper chamber is relievedas imlicatcd at and u to the draft tube so that the pressure in thischamber is substantially equal to or even less than that in the drafttube. The tendency of the centrifugal force of the water whirling in thespace between 79 and p, together with the seal it, is to reduce thepressure in the inner portion of this space below that at it, that isbelowthe pressure in the draft tube. The drop is pressure through theseal A, B, at the outer edge of the top of the runner is substantiallythe whole drop of pressure from the inlet to the draft tube.

At the bottom of the runner the seal through which the leakage must passto the draft tube is divided into two portions, A and A, the upper sealA at the bottom of the runner being relatively simple 1n form so thatonly a part of the pressure drop from inlet to draft tube occurs at thatpoint. The pressure in the chamber 1 at the bottom of the runner thusmaterially higherthan the pressure in the chan'iber between the plates0, g) at the top of the runner.

Fig. t shows a horizontal section through the axis of a single runnerhorizontal shaft turbine in which a modified embodiment of thisinvention is employed. In this arrangement the runner 15 carries thecrown plate 16 and band plate 17 having alternate grooves b and a.fitting the grooves and ribs of the stationary plates 19 and 20respectively. The two stationary plates 19, 20 are made adjustable,bolts 28, 24 being provided for screwing down the plates to dress themtoward the runner while bolts 21, 22 hold them from contact with therunner. The seals provided by the interfitting ribs and grooves aredividedinto two groups on both the crown and band of the runner, spaces25, 26 being left between the groups in which the pres sure will beautomatically regulated to maintain the runner in central position underall conditions of operation.

Between the plate 16 and the wearing ring 29 is a thin cylindricalpassage 27 providing clearance or a simple seal which necessarilyinvolves some leakage inward from the turbine intake. Following thispassage 27 along the direction of leakage flow, the thin cylindricalportion 27 opens into the wider plane annular portion 28. Thus the sizeof the passage as awhole and its direction are changed abruptly at thesame point, namely, where the portion 27 opens into the portion 28.Between the annular teeth or ribs a respectively on the runner and onthe casing, the pas sage extends in thin cylindrical form, the flowbeing in the opposite direction to that in the passage 27, and again at30 there is ail-abrupt change of direction with an increase of width.The passage then again continues through the narrow cylindrical portionbetween the ribs thence with an abrupt change of direction andenlargement to the plane annular portion 28, and so alternatelynarrowing or expanding at each change of direction. At each change ofdirection the passages are undercut a little as indicatedat 21.

Thence the passage continues through the enlarged portion 25, into theinner set of Seals which have the shape of a section of a conicalsurface cut off therefrom by two planes perpendicular to the axis andthe tortuous path through these inner seals finally terminates at thepoint 32 of low pressure in the inner chamber 33 connected to thedischarge. If the runner moves toward the head cover, it will be seenthat this wedge arrangement of the inner set of seals will cause theseseals to close and thus to restrict the flow of water on the head coverside. The clearance of the outer set of seals will remain the same forall positions of the runner. The restriction of the flow through theinner set of seals and the consequent increase of pressure produced inthe intermediate space 25 will set up a thrust upon the runher crownwhich will tend to restore the runner to its central position. A similarar-- rangementof outer and inner seals and intermediate space 26 isprovided on the runner band and if the runner should travel too far inthe opposite direction, a reduction of pressure will be caused in theintermediate space on the crown of the runner, and this, together withthe opposite action occurring against the runner band, that is, anincrease in pressure in the intermediate space against the band, willprevent the runner moving toward the draft tube. The device shown inthis figure therefore provides an automatic balance and prevents any endthrust being developed by the runner.

It will be noted that in the inner set of seals enlargements of thepassage are provided at points where the flow changes direction. This isin accordance with the principle which is followed in all of thearrangements of seals shown, that between each two points of smallclearance a space isprovided in which the flow must change both in thedirection and magnitude of its velocity, that is, the passage isenlarged at the same time that the direction of flow is altered. It

is not suflicient, for example, to provide enlargement of a passage andthen to follow this enh-irgement by a second contraction directly inline with and in the same direction as the original contraction, for insuch a de sign the water passes through the enlargement without itsvelocity being appreciably affected and without suifering a materialloss of head.

I claim 1- i 1. In a rotary hydraulic machine, a casing, a rotor withvanes therein, a conduit through the casing to deliver water to thevanes of the rotor and another such conduit to convey the water away,the casing and runner having adjacent opposed faces spaced to form apassage between them, said passage consisting of a narrow part openinginto a relatively wide part with an abrupt change of direction at thetransition, then another narrow passage extending in a directionopposite to the direction of the preceding narrow passage, and soonrepeatedly, at least two of said narrow parts with an intermediate widepafrt constituting a passage through which leakage must flow.

2. In a rotary hydraulic machine, a casing, a rotor with vanes therein,a conduit through the casing to deliver water to the vanes of the rotorand another such conduit to convey the water away, the casing and runnerhaving adjacent opposed faces spaced to form two similar passagesbetween said faces on opposite sides of the runner, each of saidpassages consisting of a narrow part opening into a relatively wide partwith an abrupt change of direction at the transition, then anothernarrow passage extending in a direction opposite to the direction of thepreceding narrow passage, and so on repeatedly. i I

3. In a rotary hydraulic machine, a casing, a rotor with vanes therein,a conduit through the casing to deliver water to the vanes of the rotorand another such conduit to convey the water away, cicuniferentialspaced ribs on the inner face of the casing and on the adjacent face ofthe runner interlocking alternately to form a leakage labyrinth, saidribs forming narrow-passages between them extending alternately inopposite directions and said ribs being undercut to give enlargements ofthe labyrinth, passage at each alternate change of direction thereof.

4. A labyrinth seal for a hydraulic machine comprising relativelyrotatable parts formed to provide a series of narrow passages extendingalternately in opposite directions and with enlarged connecting spacesbetween the ends of said passages so that the leakage water is passedwith abrupt changes of direction and eddies set up in the flow at eachsuch change of direction;

5. A labyrinth seal for a hydraulic machine comprising rotatable partson opposite sides of the rotor of said machine with passages on oppositesides of said rotor adapted to pass the leakage water in two zig zagstreams with narrow passages in alternately opposite directions andenlargements at'the places of change of direction.

6. In a hydraulic turbine in combination, labyrinth seals consisting ofa plurality of contracted passages through which the leakage waterescaping from the runner must flow in series, and alternating with saidcontracted passages enlarged passages in which the leakage fiow isdeflected; a stationary plate adjacent to the runner crownhaving acontracted running clearance at its inner periphery, and relief openingsthrough it at its outer periphery through which the leakage water canflow after passing through one of said labyrinth seals.

7. In a hydraulic turbine in combination, labyrinth seals consisting ofa plurality of contracted passages through which the leakage waterescaping from the runner must flow in series, and alternating with saidcontracted passages enlarged passages in which the leakage flow isdeflected; a stationary plate adjacent to the runner crown having-acontracted running clearance at its inner periphery, and relief openingsthrough it at its outer periphery through whichthe leakage water canflow after passing through one of said labyrinth seals, and passagesoutside of said plate leading to relief openings through the runner hubdischarging the leakage water into the centre of the turbine draft tube.

8. In a hydraulic turbine a runner forming in combination with thesurrounding s ationary parts of the turbine a plurality of contractedpassages alternating with passages which enlarge in cross-section andsimultaneously change the direction of flow, so disposed that theleakage water escaping from the runnermust flow through a series of saidpassages in succession, and means near the periphery of said runnerthrough which the leakage water can escape to a point of low pressure,after it has passed through said it? passages.

1 9.- Ina vertical shaft turbine the' combination with a runner andmeans for supplying water thereto, of means for relieving downwaterthereto, of means for relieving downward pressure on the top of therunner comprising a chamber abovethe runner and a relief opening at heouter portion ofsaid chamber leading through passages separated from therunner, followed by passages through runner crown or hub to the drafttube of the turbine.

" Q in a vertical shaft turbine the combinathereto, of means forrelieving down- "d pressure on the top of the runner comprisingstationary and rotatable surfaces forming a chamber above the runner anda relief opening at the outer portion of said chamber communicating withthe centralportion of the draft tube through a'passage extending roundsaid stationary surface and out of contact with the runner. 1

13. In a vertical shaft'turbine the com- A bination with a runner andmeans for supplying water thereto, of means for relieving downwardpressure on the top of the-runner comprising stationary and rotatablesurfaces adjacent to each other and forming a restricted chamber abovethe runner and a relief opening at the outer portion of said chamber.

14. In turbine the combination with a runner and means for supplyingwater thereto and clearance spaces at opposite sidesof said runner, oneof said spaces having a relief connection at its outer portlon and theother of said spaces having a relief connection at its inner portion andlabyrinth seals to reduce leakage into or out of said spaces.

15. In a Water turbine, a runner, a stationary part within which theperiphery of the runner rotates, a chamber above the runner,

:h a runner and means for supplying r ward pressure on the'top ofthe'runner comprising a chamber above the runner and a relief opening atthe outer portlon OfSZLlCl chamsaid chamber having a relatively freeoutlet for the water and having a tortuous passageway or labyrinth sealconstituting its inlet and located between the upper part of the runnerand the associated stationary part,

said warts and assa ew'a sbein constructed and arranged to cause thepressure above the runner to be materially less than below the same.

16. In a Water turbine, a runner, a housing enclosing the runner andhaving annular surfaces in proximity to which the peripheral part of theruner rotates, Water seals at the upper and lower portions of therunner, the seal at one point being relatively restricted, and the sealat another being relatively unrestricted.

17. In a Water turbine, a runner, a stationary part Within which therunner rotates, means forming a chamber located on the up per side ofthe runner, including a cover overlying and spaced from a top portion ofthe runner, and means forming a seal to restrict fluid flow to saidchamber, said cover being provided With a relatively free outlet Wherebyfluid in said chamber may be easily discharged.

18. In a Water turbine, a runner, a casing Within Which the runnerrotates, and clearance spaces between the runner and easing such thatleakage through one space is relatively restricted and leakage throughthe other is relatively free.

LEWIS FERRY MOODY.

CERTIFICATE or connection.

Patent No. 1,820,150. Granted August 25, 1931, to

LEWIS FERRY MOODY.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 2,line 129, for "dress" read press; page 3, line 34, for the numeral "21"read 31; and that the said Letters Patent should be read with thiscorrection therein that the same may conform to the record of the casein the Patent Office.

Signed and sealed this 17th day of November, A. D. 1931.

M. J. Moore,

(Seal) Acting Commissioner of Patents.

